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PDF AAT1142 Data sheet ( Hoja de datos )
| Número de pieza | AAT1142 | |
| Descripción | Voltage-Scaling Step-Down Converter | |
| Fabricantes | AAT | |
| Logotipo |  |
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AAT1142
800mA Voltage-Scaling Step-Down Converter
General Description
Features
SwitchReg™
The AAT1142 SwitchReg is a dynamically pro-
grammable 2.2MHz step-down converter with an
input voltage range of 2.7V to 5.5V and output from
• VIN Range: 2.7V to 5.5V
• VOUT Programmable Range: 0.6V to 2.0V
• Dynamic Voltage Management:
0.6V to 2.0V. Its low supply current, high level of
— 50mV Output Resolution
integration, and small footprint make the AAT1142
— Fast, Stable Response
the ideal choice for microprocessor core power in
• Serial Control Options:
systems such as smartphones.
— I2C Two-Wire Interface
The 2.2MHz switching frequency allows the use of
a small external inductor and capacitors. Peak cur-
rent mode control and internal compensation pro-
vide stable operation and fast voltage response
without over/undershoot or ringing.
The AAT1142 delivers up to 800mA of output current
while consuming 35µA of typical no load quiescent
current. Dynamic Voltage Management is provided
through I2C or AnalogicTech's S2Cwire™ (Simple
Serial Control™) single wire interface. The user can
program the output from 0.6V to 2.0V in 50mV steps.
— S2Cwire Single-Wire Interface
• 800mA Output Current
• Up to 93% Efficiency
• Line, Load Regulation Less Than ±0.5%
• 2.2MHz Switching Frequency
• Ultra-Small External Filter
• Low 35µA No Load Quiescent Current
• 100% Duty Cycle Low Dropout Operation
• Internal Soft Start
• Over-Temperature Protection
• Current Limit Protection
• Multi-Function MODE/SYNC Pin:
The AAT1142 optimizes power efficiency through-
out the load range via PWM/PFM mode. Pulling
the MODE/SYNC pin high enables PWM Onlywww.DataSheet4U.com
mode, maintaining constant frequency and low
•
noise across the operating range. Alternatively, the
•
— PFM/PWM for High Efficiency
— PWM Only for Low Noise
— Clock Input to Synchronize to System Clock
TSOPJW-12 or TDFN33-12 Package
Temperature Range: -40°C to +85°C
converter may be synchronized to an external
clock input via the MODE/SYNC pin. Over-temper-
ature and short-circuit protection safeguard the
Applications
AAT1142 and system components from damage.
The AAT1142 is available in a Pb-free, space-sav-
ing 2.85x3.0x1.0mm TSOPJW-12 package or a
Pb-free, low-profile 3x3x0.8mm TDFN33-12 pack-
age. The device is rated over the -40°C to +85°C
temperature range.
• Camcorders
• Cellular Phones and Smartphones
• Digital Still Cameras
• Handheld Instruments
• Microprocessor / DSP Core
• MP3, Portable Music, and Portable Media
Players
Typical Application
• PDAs and Handheld Computers
I 2C
S2Cwire*
VIN: 2.7V to 5.5V
C2
4.7µF
VIN LX
AAT1142
FB
MODE/SYNC
SDA
SCL
EN/SET
AGND
PGND
VOUT: 0.6V to 2.0V
800mA Maximum
L1
2.2µH
C1
10µF
Efficiency vs. Load
(VOUT = 1.8V)
100
90 VIN = 3.6V VIN = 2.7V
80
70
VIN = 4.2V
60
VIN = 5.0V
50
40
PWM Only
Mode
30
0 1 10 100
1000
*Optional S2Cwire or I2C Input
Output Current (mA)
1142.2006.07.1.0
1
1 page  
AAT1142
800mA Voltage-Scaling Step-Down Converter
Electrical Characteristics1
L = 2.2µH, CIN = COUT = 10µF, VIN = 3.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are
at TA = 25°C.
Symbol Description
EN/SET and MODE/SYNC
VEN/SET(L)
VEN/SET(H)
TEN/SET(L)
TEN/SET(H)
TOFF
TLATCH
IEN/SET
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
EN/SET High Time
EN/SET Timeout
EN/SET Latch Timeout
Input Low Current
VMODE/SYNC(L) Enable Threshold Low
VMODE/SYNC(H)
IMODE/SYNC
Enable Threshold High
Input Low Current
Conditions
VEN/SET < 0.6V
VEN/SET > 1.4V
VEN/SET < 0.6V
VEN/SET > 1.4V
VIN = VFB = 5.5V
Min Typ Max Units
0.6 V
1.4 V
0.3 75 µs
50 75 µs
500 µs
500 µs
-1.0 1.0 µA
VIN ×
0.4
V
VIN ×
0.7
V
-1.0 1.0 µA
Characteristics of SDA and SCL Bus Lines
Parameter
SCL Clock Frequency
Hold Time for START Condition; After
this Period, the First Clock Pulse is
Generated
LOW Period of the SCL Clock
HIGH Period of the SCL Clock
Set-up Time for a Repeated START
Condition
Data in Hold Time
Data in Set-Up Time
Set-Up Time for STOP Condition
Bus Free Time Between a STOP and
START Condition
Input Low Level
Input High Level
Symbol
fSCL
tHD;STA
Standard Mode
Min Max
100
4.0
Fast Mode
Min Max
400
0.6
Units
kHz
µs
tLOW
tHIGH
tSU;STA
tHD;DAT
tSU;DAT
tSU;STO
tBUF
VIL
VIH
4.7 1.3
4.0 0.6
4.7 0.6
0 3.45 0 0.9
350 350
4.0 0.6
4.7 1.3
VIN · 0.7
VIN · 0.3
VIN · 0.7
VIN · 0.3
µs
µs
µs
µs
ns
µs
µs
V
V
1. The AAT1142 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
1142.2006.07.1.0
5
5 Page 
AAT1142
800mA Voltage-Scaling Step-Down Converter
rate output regulation. Output regulation is main-
tained until the dropout voltage, or minimum input
voltage, is reached.
The AAT1142 achieves better than ±0.5% output
regulation across the input voltage and output load
range. Maximum continuous load is 800mA. A
current limit of 1A (typical) protects the IC and sys-
tem components from short-circuit damage.
Typical no load quiescent current is 35µA.
Thermal protection completely disables switching
when the maximum junction temperature is detect-
ed. The junction over-temperature threshold is
140°C with 15°C of hysteresis. Once an over-tem-
perature or over-current fault condition is removed,
the output voltage automatically recovers.
Peak current mode control and optimized internal
compensation provide high loop bandwidth and
excellent response to input voltage and fast load
transient events. The output voltage is stable across
all operating conditions, ensuring fast transitions
with no overshoot or ringing. Soft start eliminates
output voltage overshoot when the enable or the
input voltage is applied. Under-voltage lockout pre-
vents spurious start-up events.
Control Loop
The AAT1142 is a peak current mode step-down
converter. The current through the P-channel
MOSFET (high side) is sensed for current loop
control, as well as short-circuit and overload pro-
tection. A fixed slope compensation signal is added
to the sensed current to maintain stability for duty
cycles greater than 50%. The peak current mode
loop appears as a voltage-programmed current
source in parallel with the output capacitor.
The output of the voltage error amplifier programs
the current mode loop for the necessary peak
switch current to force a constant output voltage for
all load and line conditions. Internal loop compen-
sation terminates the transconductance voltage
error amplifier output. Loop stability and fast tran-
sient response are maintained across the entire
input and output voltage range with a small 2.2µH
output inductor and 10µF output capacitor.
Soft Start/Enable
Soft start limits the current surge seen at the input
and eliminates output voltage overshoot. When
pulled low, the enable input forces the AAT1142
into a low-power, non-switching state. The total
input current during shutdown is less than 1µA.
The turn-on time from EN to output regulation is
100µs (typical).
Alternatively, the EN/SET pin serves as the input
for S2Cwire single line control. Details of S2Cwire
operation and timing diagrams are provided in the
Applications Information section of this datasheet.
Current Limit and Over-Temperature
Protection
Switching is terminated after entering current limit
for a series of pulses to minimize power dissipation
and stresses under overload and short-circuit con-
ditions. Switching is terminated for seven consecu-
tive clock cycles after a current limit has been
sensed for a series of four consecutive clock cycles.
Thermal protection completely disables switching
when internal dissipation becomes excessive. The
junction over-temperature threshold is 140°C with
15°C of hysteresis. Once an over-temperature or
over-current fault condition is removed, the output
voltage automatically recovers.
Under-Voltage Lockout
Internal bias of all circuits is controlled via the VIN
input. Under-voltage lockout (UVLO) guarantees
sufficient VIN bias and proper operation of all inter-
nal circuitry prior to activation.
1142.2006.07.1.0
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet AAT1142.PDF ] | |
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